Screw-threading machine.



No. 727,194. V I PATENTED MAY 5, 1903.. G. M. PFAFF.

SCREW I HREADING MACHINE.

APPLI'OATIOH FILED JUNE 1; 1901.

H0 MOD-EL. 2 SHEETS-SHEET 1.

M W: EM

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N0. v727,194. PATBNTED MAY 5,- 1903. G. M. PFAPP.

SCREW THREADING MACHINE.

APPLICATION PILE'DJUNE 1, 1901. no MODEL. 2 SHEETS-SHEET 2.

x N v UNITED STATES Patented May 5, 1903.

WATENT FFICE.

SC REW-THREADING MACHINE.

SPECIFICATION forming part of Letters Patent No. 727,194, dated May 5, 1903'. Application filed June 1,1901. Serial No. 62,736. (No model.)

To all whom, it may concern:

Be it known that I, GEORG MICI-IAEL PFAFF, a subject of the King of Bavaria, residing in the city of Kaiserslautern, Kingdom of Bavaria, German Empire, have invented certain new and useful'Improvements in*Screw Threading Machines, of which the following is a specification.

This invention relates to screw-threading machines for making male threads, and has for its object to remedy the objections found in the hitherto-employed threadingdevices viz., that the catches which serve to release the dies intermittently engage with each other, even after the thread has been cut to the desired length. This is due to the fact that the dies remaining in engagement with the finished screw-bolt revolve with the latter because the rotatory movement of the screwbolt cannot be at once stopped owing to the centrifugal power of the revolving parts of the machine. In consequence of this intermittent engagement of the catches with each other the dies continue to thread the bolt above the desired length, so that the work is improperly done, and frequently the head of the screw-bolt is broken off. Further, the catches wear off very quickly, and the whole machine suffers dangerous shocks. Much trouble is also experienced in removing the bolt from within the dies, particularly when the latter are made of a single piece. In the present invention this objection vislremoved by the arrangement of yielding catches,which' after the thread has been cut to the desired length and when the longitudinal movement of the dies has changed to rotation do not interfere with each other when cominginto engagement.

In the accompanying drawings, Figure 1 is a side elevation of a screw-threading machine to which my improvement is applied. Fig. 2 is a longitudinal section of the die-holder, the latter being in the position shortly before the threading operation begins. Fig. 3 is a similar partial section, the die-holder being in position at the moment of release of the dies, at which the catches intermittently touch each other. Fig. 4 is a cross-section on line I I, Fig. 2. Fig. 5 is a cross-section on line II II,

Fig. 2, as seen in the direction of arrow III;

and Fig. 6 a similar section as seen in the direction of arrow IV. v

The new cutting or threading-device is provided with one or several catches, consisting.

of a pin 02, having a head 'L'and secured to the die-holding head I) by means of a set-screw k. Acap Z under theinfluence of a coiled spring m, which has the tension to press the cap outward, embraces the pin 02. This cap is held against escapement from above the pin 02 by means ofashoulderoresting upon the head 2' of the pin.v The cap Znormally projects beyond the head 7; and is provided with a beveled edge The spindle p of the head 19 is guided in a casing 'q, having a head r. This casing is, as seen in Fig. 1, secured in a boring of the support t of the screw-machine, so as not to be movable: therein. The spindle p of the head 19, carrying the dies, is adapted to move longitudinally within the casing q and can rotate therein in one direction only 1 6., in the direction of the rotatory movement of the threaded bolt. It is prevented from rotating in the reverse direction by a pin 'Lb, mounted on a spring 2; in a boring w of the spindle '19. As shown in Fig. 4, this pin is beveled and projects under the influence of thespring 0) into a correspondinglyshaped groove of the casing q, thus allowing a rotation of the spindle in the direction mentioned above. In the head 0 of the casing q is arranged a catch, consisting of a pin g, that rests with its back upon a leaf-spring f, attached to head 1'.

The operation is as follows: The threading device is advanced toward the work to be cut by means of the support 25 until the dies enthreading operation is illustrated in Fi 3.

As the finished work cannot be at once stopped or reversed in order to release the dies owing to the momentum of the revolving parts of the machine, and as the dies are still in engagement With the finished work, the dies begin to rotate with this work, the pins g The position of the catches having cleared the caps Z. The consequence is that the catches of the head I) and those of the head 1' will intermittently touch each other, but being yielding, as above described, will give way and will have no eifect upon the rotating dies-that is to say, will not cause a further threading of the Work. In the meantime the revolving parts as well as the work will be reversed, and as the spindle [O p is not allowed by the pin u to rotate in the projecting beyond the pin, means for holding the cap to the pin, a fixed head, and a pin projecting from said head into the path of the beveled cap, substantially as specified.

2. In a screw-threading machine, the combination of a rotatable die-holding head with a pin projecting therefrom, a slidable springinfluenced cap having a beveled edge and projecting beyond the pin, means for holding the cap to the pin, a fixed head having a perforation, and a spring-influenced pin engaging said perforation and arranged within the path of the beveled cap, substantially as specified.

In witness whereof I have hereunto signed my name in the presence of two subscribing witnesses.

GEORG MICHAEL PFAFF.

Witnesses:

MICHAEL ZIMMERMANN, KARL HEBACH. 

